Fix compilation error with C23 #312

Job	Run time
ruby-versions / Generate Ruby versions	3s
ubuntu-20.04 2.3	36s
ubuntu-20.04 2.4	36s
ubuntu-20.04 2.5	36s
ubuntu-20.04 2.6	37s
ubuntu-20.04 2.7	38s
ubuntu-20.04 3.0	30s
ubuntu-20.04 3.1	32s
ubuntu-20.04 3.2	30s
ubuntu-20.04 3.3	32s
ubuntu-20.04 head	21s
ubuntu-20.04 jruby	1m 13s
ubuntu-20.04 jruby-head	1m 22s
ubuntu-22.04 2.3	35s
ubuntu-22.04 2.4	30s
ubuntu-22.04 2.5	39s
ubuntu-22.04 2.6	42s
ubuntu-22.04 2.7	36s
ubuntu-22.04 3.0	29s
ubuntu-22.04 3.1	35s
ubuntu-22.04 3.2	31s
ubuntu-22.04 3.3	33s
ubuntu-22.04 head	22s
ubuntu-22.04 jruby	1m 9s
ubuntu-22.04 jruby-head	1m 7s
macos-12 2.3	1m 17s
macos-12 2.4	1m 1s
macos-12 2.5	1m 12s
macos-12 2.6	59s
macos-12 2.7	57s
macos-12 3.0	38s
macos-12 3.1	36s
macos-12 3.2	56s
macos-12 3.3	34s
macos-12 head	26s
macos-12 jruby	1m 11s
macos-12 jruby-head	1m 48s
macos-13 2.3	59s
macos-13 2.4	1m 45s
macos-13 2.5	1m 11s
macos-13 2.6	1m 6s
macos-13 2.7	1m 1s
macos-13 3.0	35s
macos-13 3.1	38s
macos-13 3.2	1m 26s
macos-13 3.3	40s
macos-13 head	35s
macos-13 jruby	2m 18s
macos-13 jruby-head	1m 18s
macos-14 2.6	38s
macos-14 2.7	31s
macos-14 3.0	20s
macos-14 3.1	25s
macos-14 3.2	21s
macos-14 3.3	20s
macos-14 head	15s
macos-14 jruby	43s
macos-14 jruby-head	40s
windows-latest 2.3	1m 27s
windows-latest 2.4	3m 3s
windows-latest 2.5	3m 58s
windows-latest 2.6	3m 49s
windows-latest 2.7	3m 36s
windows-latest 3.0	3m 3s
windows-latest 3.1	3m 2s
windows-latest 3.2	2m 32s
windows-latest 3.3	3m 9s
windows-latest head	3m 2s
windows-latest mswin	3m 8s
ubuntu-latest jruby-9.3	1m 6s
ubuntu-latest jruby-9.4	1m 2s
macos-latest truffleruby-head	1m 35s
ubuntu-latest truffleruby-head	1m 16s
	1h 24m 2s

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